The invention concerns a coin checking device.
In known coin checking devices the diameter of the coin is checked either mechanically or inductively. The mechanical checking is done according to the principle applied to the usual caliper gauge, for example by dimensioning the coin slit such that coins whose diameter exceeds an upper limit cannot pass and the slanted coin channel has a side window through which coins fall which are smaller than a lower limit value. (EP-A2-0 122 732). This requires for each acceptable coin type a separate, fitting coin slit and a separate coin channel with an individually fitted window. The refitting of the coin slit and the channal from one diameter range to another is expansive and an actual diameter measuring is not possible in this manner. For inductive checking the coin influences the field with a high-frequency excited coil in one measurement, dependent on the coin diameter, from which an analog signal is obtained that indicates if the coin has the diameter of the coin to be accepted (U.S. No. Pat. 4,108,296). The refitting from one diameter range to another is also expensive, even if the signal is changed from analog to digital and evaluated by a microprocessor; because of the stray field of the coil there is no linear connection between the coin diameter and the signal size so that the coin checker cannot be simply programmed for another coin diameter. It is much rather necessary to first empirically determine the signal size assigned to the other coin diameter and reprogram according to this dimension.
The invention provides relief for this. The invention solves the problem by creating a coin checking device which supplies a mathematically defined control value dependent on the distance of the sensor when contacting the coin edge.